The present invention relates to a specific gravity indicator used for measuring the specific gravity of an aqueous liquid. More particularly, it relates to a specific gravity indicator which is used to measure the specific gravity of an aqueous liquid, particularly urine, by observing the status of the indicator in the liquid, namely, whether the indicator floats on the surface of the liquid, sinks into the liquid or suspends stationarily in the liquid without sinking and floating.
There is an areometer as one of simple specific gravimeter used for measuring the specific gravity of liquid. The measurement of specific gravity using the areometer has a problem that the measurement must be performed at a specified temperature, for instance, 20.degree. C., which results in need of thermostat and troublesome operation.
In the past, the areometer was used for measuring the specific gravity of urine but is not used at present for the reasons mentioned above.
The common method used at present for determining the specific gravity of urine is one wherein the refractive index of urine is measured. The method utilizes the principle that the refractive index of urine is proportional to the total concentration of the urea, sodium chloride and potassium chloride contained in urine. Those substances are main components of urine. However, the ratio of the amount of urea to the total amount of sodium chloride and potassium chloride in urine varies every sample. For instance, in the case of the urine collected from a man who has eaten a salty food, the proportion of sodium salt is increased. Therefore, the error resulting from a deviation of the above-mentioned ratio from that of the standard urine is inherent in the method for determining the specific gravity of urine by measuring its refractive index. Furthermore, the method is not necessarily an easy method due to the need of refractometer.
The urine analysis is conducted with patients suffering from various diseases such as nephropathy and diabetes and post-operative patients. In that case, usually, urine is collected in a urinary drainage bag. It is convenient if there is a means for directly measuring the specific gravity of a urine collected in the urinary drainage bag.